I haven't tried Fluent yet, but—in theory—could you not have both the message identifier and the original string in your code?

Their React example kind of points towards this: https://github.com/projectfluent/fluent.js/wiki/React-Bindin...

They provide a <Localized> component, which has an identifier and wraps a piece of markup containing the original:

  <Localized id="hello">
      <h1>Hello, world!</h1>
  </Localized>

Seems like the best of both worlds.